1. Field of the Invention
The present invention generally relates to a multipoint videoconference system, and in particular to a picture combining method and apparatus in a multipoint control unit for use in the multi-point videoconference system.
2. Description of the Related Art
A multipoint videoconference system performs multipoint teleconferencing using the ITU-T H.261 xe2x80x9cVideo Codec for Audiovisual Services at pxc3x9764 kbit/sxe2x80x9d standards and the narrow band ISDN (Integrated Services Digital Network) channels for signal transmission. The multipoint videoconference system includes a multipoint control unit and a plurality of videoconference terminals, which are individually located in the places and are connected to one another, for example, through the ISDN network.
In such a multipoint videoconference system, the multipoint control unit receives terminal picture data signals from the videoconference terminals through the ISDN network and provides a combined picture data signal to each of the videoconference terminals through the ISDN network. Each of the videoconference terminals displays a combined picture including a plurality of divisional pictures by the use of a split screen technique in response to the combined picture data signal.
A conventional multipoint control unit is provided with a plurality of decoders individually corresponding to the videoconference terminals, which decodes terminal picture data signals received from the videoconference terminals to produce decoded terminal picture signals according to H.261 xe2x80x9cVideo Codec for Audiovisual Services at pxc3x9764 kbit/sxe2x80x9d.
However, the conventional multipoint control unit must carry out the decoding of terminal picture data signals received from the videoconference terminals to produce the combined picture data signal. Therefore, it is necessary to provide the multipoint control unit with as many decoders as the videoconference terminals, resulting in the increased amount of hardware.
An object of the present invention is to provide a picture combining method and apparatus allowing the amount of hardware of a multipoint control unit to be reduced.
Another object of the present invention is to provide a picture combining method allowing simplified picture combining.
According to the present invention, an apparatus for generating a combined picture data signal in a multipoint control unit of a videoconference system having a plurality of videoconference terminals, wherein the combined picture data signal provides each of the videoconference terminals with a partitioned display screen having separate portions corresponding to respective ones of the videoconference terminals, includes: an extractor for extracting an intra-frame coding picture from each of terminal picture data signals received from the videoconference terminals; and a combiner for combining intra-frame coding pictures extracted from the terminal picture data signals to produce the combined picture data signal.
The extractor may include an intra-frame separator for separating an intra-frame coding picture from each of the terminal picture data signals by detecting a picture frame followed by the intra-frame coding picture from the terminal picture data signal; and a frame memory for storing the intra-frame coding picture, which is updated every time a picture frame is detected.
The combiner may include: a header separator for separating each of the terminal picture data signals into an intra-frame video data and header data; a header generator for generating combined header data based on header data of the terminal picture data signals; and a multiplexer for multiplexing intra-frame video data of the terminal picture data signals and the combined header data to produce the combined picture data signal.
Each of the videoconference terminals may conform to ITU-T H.320 standard (Narrow-band Visual Telephone Systems and Terminal Equipment). The intra-frame coding picture may be a frame of QCIF (Quarter Common Intermediate Format) video data.
According to another aspect of the present invention, a method for generating a combined picture data signal in a multipoint control unit of a videoconference system having a plurality of videoconference terminals, has the steps of: a) extracting an intra-frame coding picture from each of terminal picture data signals received from the videoconference terminals; and b) combining intra-frame coding pictures extracted from the terminal picture data signals to produce the combined picture data signal.
As described above, only an intra-frame coding picture is extracted from each of the terminal picture data signals received from the videoconference terminals. Therefore, a frame of combined picture data can be formed from the intra-frame coding picture without the need of H.261 video data decoders conforming to H.261 (Video codecs for audiovisual services at pxc3x9764 Kbps), resulting in dramatically reduced amount of circuit hardware in the multipoint control unit. Since only intra frames are used, smoothly moving picture cannot be displayed but still pictures, each of which is divided into portions corresponding to individual videoconference terminals on each vldeoconference terminal.